DarthPuppy wrote:And I hear you about the durability. A long time ago before I became more aware of the environmental issues, I had a diesel. They are very efficient, durable and require little maintenance. They definitely are very appealing until you know the downsides for air quality.
Getting back on topic about diesels, I wonder how this would affect commercial vehicles in Germany. The title says "older diesel cars". What about diesel trucks. They also run off the lean, NOx producing diesel cycle. And commercial companies use big diesel vehicles because of their economic benefits, reliability and longevity.
On the other hand, I still don't see why technology can't fix this. Doing research, diesel engines used to produce less NOx than gasoline cars did back before EFI and catalytic converters. But like other any other lean burn technology, it is hard to get rid of NOx when there is lots of oxygen and nitrogen present in the exhaust.
Doing some math, I once figured out how much oxygen flow my engine would need. I also found an oxygen separator that could put out that much oxygen and used less than 1hp. The idea was to cool the exhaust, feed that into the intake, and add the oxygen necessary. No nitrogen, no NOx! The problem is that the separator is very big and would take up both the rear seat and trunk area. It was also expensive. And I'd probably need a bigger radiator to cool the exhaust properly.
If NOx can be eliminated, then things that could make major increases in efficiency could be implemented, like higher compresión ratios, advanced injection timing and no more EGR. The same technology could also be used on gasoline engines, allowing for highly efficient, lean burning, direct injection engines.